Traditional relativistic magnetrons used for HPM generation suffer from several limitations that reduce their effectiveness and/or efficiency. Among these limitations are 1) very high voltage operation, 2) small cathode surface area, 3) high axial confining magnetic field, 4) large device size, 5) inefficient mode conversion, and 6) downstream current loss.
High voltage operation and small cathode surface area share a relationship that has historically proven to be problematic. For a relativistic magnetron, HPM generation may only occur if high electromagnetic power (of the order of Gigawatts) is delivered to the device. For relativistic magnetrons, a pulsed power system is typically utilized to deliver this power. However, for field emitting cathodes, the electric current emitted is limited by the cathode surface area. For a standard relativistic magnetron, this cathode must be smaller than the outer hull of the device where the anode/slow wave structure is located. Consequently, for high electromagnetic power P to be delivered to the magnetron, high voltages V must be used to compensate for the limitations on current I (P=IV).
In a standard relativistic magnetron, confinement of the electron beam typically requires a magnetic field ranging from 0.12-0.32 T. Traditionally, Helmholtz coils have been used to provide this field, thus the power burden of an HPM system includes the energy necessary to generate the current in the coils. The inefficiency of input energy versus output has been a debilitating factor in traditional magnetrons.
Magnetron size has also been a limiting factor for HPM system deployment and use. Relativistic magnetrons used in traditional HPM systems typically exceed a 10 cm radius, thus presenting a logistical challenge to their deployment on compact mobile platforms. The size problem of traditional relativistic magnetrons is compounded when the magnetron's radio frequency (RF) extraction method is considered. Standard relativistic magnetrons extract radially through one or more of the resonant cavities of the device. This often results in a network of slots and waveguides that further increase the size and weight of the device. Additionally, when multi-slot RF extraction schemes are used, a combiner and mode converter are used to combine the RF signal. This additional componentry increases the size and weight of traditional HPM systems.
Another problem with traditional HPM systems is downstream current loss. Leakage of current beyond the magnetron interaction region degrades performance and may suppress oscillation.
A need exists for a magnetron design that reduces the necessary magnitude of the magnetic field and causes a reduction on the power requirements of the entire HPM system. Furthermore, advances in magnetron design are desirable that result in a compact implementation that delivers HPM radiation with minimal current loss (efficiency).
This background information is provided to reveal information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention.